System for the automatic control of airplanes



E. FISCHEL Feb. 20, t

SYSTEM FOR THE AUTOMATIC CONTROL OF AIRPLANES Filed Sept. 4, 1935 um IAttorneys.

Patented Feb. 20, 1940 U N I I'ED E S PATENT I OFFICE SYSTEM FOR THEAUTOMATIC CONTROL .OF AIRPLANES Application September 4, 1935, SerialNo. 39,120 In Germany September 24, 1934 13 Claims.

My invention relates to a system for the automatic control of airplanes,and particularly to means which permit to maintain the position and thespeed of flight at a desired value without exposing the airplane to anydanger.

Attempts have already been made to effect both a stabilization of thespeed of flight and a stabilization of the position by means of theelevator. It is, however, evident that only one of these stabilizingeffects may be attained with the aid of the elevator alone. In the firstcase the position of the airplane with respect to the transverse axis issubjected to changes whereas, on the other hand, the advantage isattained that the speed of the airplane is automatically maintainedsubstantially constant. In the second case the longitudinal axis of theairplane is maintained automatically horizontal, which is in some casesdesirable. In this case, however, the pilot is compelled to control thespeed of the airplane. If this is overlooked and the speed drops below apredetermined value troubles may arise and under certain circumstanceseven a crash of the airplane may occur.

The object of the present invention is to overcome the above drawbacksby employing besides the elevator also the driving gear "for the controland by making the elevator as to its adjustment dependent upon aclinometer, and the device for controlling the power of the driving geardependent as to its adjustment upon a speedometer.

Another object of my invention consists in stabilizing the height offlight by making the adjustment of the driving gear dependent upon aspeedometer and the adjustment of the elevator dependent upon aclinometer and an altimeter.

Another objectof my invention consists-so as to maintain the position,the speed and the height of the airplane constantin making theadjustment of the elevator dependent upon a clinometer and an altimeterand the adjustment of the driving gear dependent upon a speedometer andan altimeter, for which purposes the same altimeter may be employed.

Another object of my invention consists in causing an altimeter togetherwith a speedometer to act constantly on the control of the driving gearand, in the case of the height differing considerably from the desiredvalue, causing an altimeter further to act on an elevator which isconstantly influenced by a clinometer.

still another object of my invention consists in provisions whereby inthe case of the driving gear power falling below a predetermined value aspeedometer is caused to act on the elevator which in the case of anormal driving gear power is influenced by a clinometer. 5

Further details of my invention will be apparent from the followingdescription in connection with the accompanying drawing whichillustrates by way of example a system embodying my invention.

In the drawing l denotes a clinometer. for instance, a gyroscopicclinometer which is mounted in the airplane in such a manner that aninclination of the airplane about its transverse axis is indicated by adeflection of the indicator 2 relatively to the support 3 secured to theairplane which indicator is connected to one of the cardan shafts of the'gyroscopic clinometer. The indicator 2 is designed in the form of acontact arm and the end-- thereof slides over a resistance 4 whosecarrier may be shifted in longitudinal direction with theaid of twomagnets 5 and 6 for a purpose hereinafter described. If the two magnets5 and 6 are not energized the carrier assumes under the influence of thetwo springs 'l and 8 the central position shown. If the longitudinalaxis of the airplane is in the horizontal position the contact arm 2contacts with the center of the resistance 4, provided that the magnets5 and 6 are not energized.

By means of the differential coil arrangement shown, the position of thecontact arm 2 relatively to the resistance 4 is caused to give acorresponding angular position to a movable magnet 9 which in the usualmanner acts, if desired, together with a turn indicator l0, through adifferential lever II on the adjusting device, i. e., on the rudderactuating device 12 (servomotor) for the elevator I3. Since the rudderactuating device is in itself generally known the details thereof neednot be fully described. l4 denotes a speedometer well known in the artand comprises a diaphragm I5 within a casing. The impact pressure of therelative wind acts on the one side of this diaphragm while the otherside thereof is under the influence of an opposing force which isproduced by a spring I6 as disclosed in the drawing and which may beadjusted by a mechanical, electrical, or, if desired, by a wirelesstransmission system. In the drawing an adjustment by hand is shown. Thetension of the spring; is adjusted by turning the crank 46 to rotate theflexible shaft 4'! connected with said spring, and the amount of suchtension maybe read off from a scale 48. The relative wind speedindicator is connected through a rod l! to a differential lever 18 whichin turn acts on the control arm 19. The latter plays with one endthereof between two counter-contacts whose carrier 20 is as hereinafterdescribed adjustable by means of a worm wheel segment and a worm 2|. Anelectric or hydraulic servomotor 22 is controlled by means of, thecontact arm 19 and the contacts of the carrier 20, the servomotor 22acting on the adjusting lever by way of a worm gear 23-and anintermediate lever 24 and adjusting with the aid of the lever 25 adevice for controlling the driving power control gear for instance athrottle.

As will be apparent from the above the system so far described issufiicient to produce the result for which my invention has beendesigned. As will be seen from the drawing the carrier 20 on which thetwo contacts for the control arm l9 are mounted is coupled to theservomotor 22 through the worm 2| and a bevel gear 26. In this manner afollow-up action is attained, by which the power is regulated in one orthe other sense only to .the extent to which the control arm I9 is movedin one or the other sense in accordance with its operating mechanismdescribed.

As above mentioned an altimeter is connected according to the inventionwith respect to the adjusting device for the elevator H in parallelrelation with the clinometer I. The altimeter which may be of anysuitable type is shown as a so-called statoscope 21 and is provided asin the case of the speedometer with a diaphragm 28 which closes anevacuated chamber and, consequently, adjusts itself in accordance withthe atmospheric pressure and, therefore, in accordance with thealtitude. The diaphragm may be biased by a spring 29, thus rendering itpossible to predetermine the desired altitude of an airplane. Theadjustment of the spring 29 may be effected. by hand with the aid of thecrank 30 according to the scale 3! or also with the aid of a remotetransmitting system; for instance, of a wireless receiving set. Thelatter consists of an aerial 32 to which two oscillation circuits 33 and34 are connected which are tuned to two different waves. The voltagesappearing at the ends of the oscillation circuits are rectified by meansof the'detectors 35 and 36 and actuate the relay 3'! or respectively inaccordance with the length of the waves emitted from the transmitter.These relays close the circuits leading from an energy source 39 to areversible motor 40 which efiects the adjustment of the spring 29arranged in the statoscope 21. A differential gear 4| permits theadjustment of the spring either manually or wirelessly as well as byboth methods independently of one another.

The altimeter thus adjusted to its desired value acts on the elevator asfollows: The lever 42 carries a contact which comes into engagement witha counter-contact 43 or 44 depending upon the difference of the altitudeof flight from the desired value. In this manner a circuit fed by theenergy source 45 is closed,'which circuit energizes either theelectromagnet 5 or 6 and thus shifts the carrier of the resistance 4 inthe bearings thereof, so that a corresponding movement of the movablemagnet 9 and, therefore, of the elevator I3 is attained by theadjustment of the resistance 4 relatively to the contact arm 2.independently of the movement of the gyroscope. When the airplane hasbeen brought back to the desired altitude by these instrumentalities,the magnet circuit will be broken and the rudder returns to its positionof rest.

In short, the operation of the system is as 5 follows: The desiredaltitude is set by means of the remote transmitting system 32-49 or ofthe crank 30. Furthermore the desired speed of flight is set on thescale 48 with the aid of the crank 46, in addition to which a remotetransfer system may, of course, also be provided. The airplane will thenoperate according to the desired values so set. As soon as the latterare obtained the speedometer l4 takes care of maintaining the desiredspeed and the altimeter 21 causes the airplane to maintain the properaltitude. At the same time the clinometer l stabilizes the position ofthe longitudinal axis of the airplane. If a different desired altitudeis set with the aid of the crank 30 or of the remote transmitting system3239 or if for any reason the altitude of the airlane differsconsiderably from the desired value, then the control arm 42 comes intoengagement with one or the other of the counter-contacts 43, 44 andthereby shifts the resistance 4 in the corresponding direction with theresult that the airplane assumes the suitable inclination so as toovercome the difference in altitude.

According to another feature of the invention the control of the drivinggear power may also be made dependent upon the position of theabove-described altimeter or an altimeter of any other suitable type. Tothis end, the lever 42 of the statoscope 21 is connected to thedifferential lever l8, to the other end of which as above described isconnected the speedometer In this manner, the altimeter controls thedriving gear continuously, whereas only an impulse is transmitted to theelevator if the actual altitude of flight differs from the desiredaltitude by a given amount.

According to still another feature of my in-l. vention, the entirestabilization is taken care of by the speedometer and elevator, if thepower 45 of the driving gear decreases below a predetermined value. Asabove described, it involves dangers to stabilize the airplane chieflyas to its position, if owing to a decrease in power of the driving gear,the speed decreases below a predetermined value. In order to change overthe speedometer control. of the driving gear to the control of theelevator in such a case a switch 49 is provided which is thrown over ifthe speed of the driving motor falls below a predetermined value. Thechanging over of the switch 49 may be eiTected by a centrifugal governor50 actuated .by the driving motor. After this change over the movablemagnet 9 is no longer connected to the resistance 4, but to theresistance 5|, over which a sliding brush 52 connected to the rod 11 ofthespeedometer i4 is shifted in accordance with the speed of flight.

It is to be understood that it is not necessary that the altimeter,speedometer and clinometer designated as measuring instruments beprovided with indicating scales, since it is sufiicient for theautomatic control, if the measuring devices merely control without anyindication being given.

I claim as my invention:

1. In a system for the automatic control of aircraft, an elevator, analtimeter and a clinometer, means for controlling said elevator andinterconnected with said altimeter and clinometer 75 to produce aresultant control value in response.

to the altimeter and clinometer reactions for adjusting the elevator forthe desired altitude and inclination of the craft, a driving powercontrol forsaid craft and means connected with said altimeter and saiddriving power control for exerting upon the driving power control anadditional resultant control force commensurate with the resultantaltimeter and clinometer control reactions upon the elevator torestabilize the craft in inclination and speed during variations inaltitude.

2. In a system for the automatic control of aircraft, an elevator, analtimeter and a clinometer, means for controlling said elevator andinterconnected with said altimeter and clinometer to produce a resultantcontrol value in response to the altimeter and clinometer reactions foradjusting the elevator for the desired altitude and inclination of thecraft, a driving power control for said craft and means reactive to therelative speed of the craft and interconnected with said altimeter andwith said driving power control for exerting upon the driving power anadditional resultant control force commensurate with the resultantaltimeter and clinometer control reactions upon the elevator torestabilize the craft in inclination and speed during variations inaltitude.

3. In a system for the automatic control of aircraft, an elevator, analtimeter and a clinometer, means for controlling said elevator andinterconnected with said altimeter and clinometer to produce a resultantcontrol value in response to the altimeter and clinometer reactions foradjusting the elevator for the desired altitude and inclination of thecraft, means reactive to the relative speed of the craft, means forcontrolling the driving power of the craft and a difierential connectionbetween said two last mentioned means for exerting upon the drivingpower a control value resulting from the speed responsive means andaltimeter reactions and commensurate with the resultant altimeter andclinometer reactions upon the elevator, to restabilize the craft ininclination and speed during variations in altitude.

4. In a system for the automatic control 01' aircraft, an elevator and aservometer for operating said elevator, an altimeter, a clinometer and acontrol element responsive to the combined reactions of said altimeterand clinometer for imposing upon said servomotor a resultant controlvalue tending to adjust the elevator'for .the desired altitude andinclination of the craft,

a speedometer, a servomotor for controlling the driving power of the.craft and a differential lever connection between said speedometer andsaid altimeter and operatively associated with said power servometer forimposing upon said, servomotor a control effect resulting from thecombined speedometer and altimeter reactions and commensurate with theresultant altimeter and clinometer reactions upon the elevatorservomotor to restabilize the craft in inclination and speed duringvariations in altitude.

5. In a system for the automatic control of aircraft, an elevator and aservomotor for operating said elevator, an altimeter, a clinometer and acontrol element responsive to the combined reactions of said altimeterand clinometer for imposing upon said servomotor a resultant controlvalue tending to adjust the elevator for the desired altitude andinclination of the craft, a speedometer, a servomotor for controllingthe driving power of the craft and a difierential lever connectionbetween said speedometer and said altimeter and operatively associatedwith said power servomotor for imposing upon said servo motor a controlefl'ect resulting from the combined speedometer and altimeter reactionsand commensurate with the resultant altimeter and clinometer reactionsupon the elevator servomotor to restabilize the craft in inclination andspeed during variations in altitude, and switching means for the controlelement of the elevator servomotor for transferring the elevator controlfrom the joint altimeter and clinometer control to the joint altimeterand speedometer control in case the driving power decreases below adesired value.

6. In a system for the automatic control of aircraft, an elevator and aservomotor for operating said elevator, an altimeter, a clinometer and acontrol element responsive to the combined reactions of said altimeterand clinometer for imposing upon said servomotor a resultant controlvalue tending to adjust the elevator for the desired altitude andinclination of the craft, a speedometer, a servomotor for controllingthe driving power of the craft and a differential lever connectionbetween said speedometer and said altimeter and operatively associatedwith said power servomotor for imposing upon said servomotor a controleffect resulting from the combined speedometer and altimeter reactionsand commensurate with the resultant altimeter and clinometer reactionsupon the elevator servomotor to 'restabilize the craft in inclinationand speed during variations in altitude, and switching means for thecontrol element of the elevator servomotor, responsive to the revolutionmember of the driving engine of the craft, for transferring the elevatorcontrol from the joint altimeter and clinometer control to the jointaltimeter and speedometer control when the engine speed drops below adesired value.

7. In a system for the automatic control of aircraft, an elevator, analtimeter, a clinometer and means for controlling said elevator jointlyfrom said clinometer and altimeter, said means comprising a movablecontact arm operatively connected with said clinometer to respond to thelatters reactions to inclination variations of the craft, a resistanceover which said contact arm is arranged to slide, a movableelectromagnet arranged to actuate said elevator and a source of currentconnected in circuit with the coils of said magnet, with said contactarm and with said resistance to move the electromagnet in accordancewith the resistance values adjusted by said contact arm due to thereactions of said clinometer, means connected with said altimeter forvarying the position of said resistance with respect to the slidingdirection of said contact arm to embody in the control of said movableelectromagnet the altitude reactions of said altimeter, a driving powercontrol for the craft and means connected with said altimeter and saidpower control for exerting upon the driving power an additional controlforce commensurate with the resultant altimeter and clinometer controlreactions upon the elevator, to restabilize the craft in inclination andspeed during variations in altitude.

8. In a system for the automatic control of aircraft, an elevator, analtimeter, a clinometer and means for controlling said elevator jointlyfrom said clinometer and altimeter, said means comprising a movablecontact arm operatively connected with said clinometer to respond to thelatterfsreactions to inclination variations of the craft, a resistanceover which said contact arm is arranged to slide, a movableelectromagnet arranged to actuate said elevator and a source of currentconnected in circuit with thecolls of said magnet, with said contact armand with said resistance to move the electromagnet in accordance withthe resistance values adjusted by said contact arm due to the reactionsof said clinometer, means connected with said altimeter for varying theposition of said resistance with respect to the sliding direction ofsaid contact arm to embody in the control of said movable electromagnetthe altitude reactions of said altimeter, a driving power control forthe craft, means reactive to the relative speed of the craft andinterconnected with said altimeter and said driving power control forexerting upon the driving power an additional control force resultantfrom the reactions of said altimeter and speed-reactive means, andcommensurate with the resultant altimeter and clinometer controlreactions upon the elevator, to restabilize the craft in inclination andspeed during variations in altitude.

9. A method of stabilizing aircraft during altitude variationsconsisting of controlling the craft elevator by a control force composedfrom a plurality of control forces responsive to altitude andinclination, and simultaneously imposing upon the power control of thecraft an increment of control force composed from aforesaid altituderesponsive control force and a craft speed responslve control force andof sumcient value to vary the speed of the craft commensurate with theeffect produced by the resultant elevator control force upon theelevator.

10. A method of stabilizing aircraft during altitude variationsconsisting of controlling the craft elevator by a control force composedor control forces responsive to altitude and inclination andsimultaneously controlling the craft power in accordance with the efiectof said firstnamed force by a force responsive to craft speed and tosaid altitude.

11. A method of stabilizing aircraft during altitude variationsconsisting of controlling the craft elevator by an impulse which is acombi nation of impulses responsive to altitude and to inclination, andsimultaneously controlling the craft power by an impulse responsiveto'said altitude. V V

12. A method of stabilizing aircraft during a1- titude variationsconsisting of controlling the craft elevator by an impulse which is acombina tion of impulsesresponsive to altitude and to inclination, andsimultaneously controlling the craft power by an impulse which is acombination of impulses responsive to craft speed and to said altitude.

13. A method of stabilizing aircraft during altitude variationsconsisting of controlling the craft elevator by impulses responsive toaltitude and inclination and simultaneously controlling the craft powerby impulses responsive to speed and to said altitude.

EDUARD FISCHEL.

